1. Field of the Invention
The present invention relates to an organic light-emitting diode (OLED), and more particularly to a candlelight-like light organic light-emitting device with high efficiency, high color rendering index (CRI) and low color temperature (CT).
2. Description of the Prior Art
An organic light emitting diode (OLED) was invented by C. W. Tang and S. A. VanSlyk et al. of Eastman Kodak Company in 1987 and manufactured by a vacuum evaporation method. A hole transporting material and an electron transporting material (such as Alq3) are respectively deposited on a transparent indium tin oxide (abbreviated as ITO) glass, and then a metal electrode is vapor-deposited thereon to form the self-luminescent OLED apparatus. Due to high brightness, fast response speed, light weight, compactness, true color, no difference in viewing angles, no need of liquid crystal display (LCD) type backlight plates as well as a saving in light sources and low power consumption, it has become a new generation display.
In addition to light-emitting material layers, the conventional OLED device is often added to other intermediate layers, such as an electron transport layer and a hole transport layer, so as to enhance the efficiency of the OLED device. Referring to FIG. 1, which is a structural drawing of a conventional OLED device. As shown in FIG. 1, the conventional OLED device 1′ includes a cathode 11′, an electron injection layer 12′, an electron transport layer 13′, a first light-emitting material layer 14′, a second light-emitting material layer 15′, a hole transport layer 16′, a hole injection layer 17′, and an anode 18′.
The above-mentioned conventional OLED device 1′ is a high efficiency OLED device; however, it is a white light OLED device and merely adapted to be a lighting source. This OLED device 1′ is unsuitable for being a reading light or a bedside light because the high brightness and high color temperature of the white light would induce discomfort on human eyes, and more seriously, the high brightness and high color temperature of the white light would suppress the secretion of melatonin, so as to cause human insomnia.
Accordingly, in view of the conventional OLED devices still have shortcomings and drawbacks, the inventor of the present application has made great efforts to make inventive research thereon and eventually provided a candlelight-like light organic light-emitting device.